Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to performing synchronization between nodes in a wireless communication systems.
Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems, and single-carrier frequency division multiple access (SC-FDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. For example, a fifth generation (5G) wireless communications technology (which can be referred to as 5G new radio (5G NR)) is envisaged to expand and support diverse usage scenarios and applications with respect to current mobile network generations. In an aspect, 5G communications technology can include: enhanced mobile broadband addressing human-centric use cases for access to multimedia content, services and data; ultra-reliable-low latency communications (URLLC) with certain specifications for latency and reliability; and massive machine type communications, which can allow a very large number of connected devices and transmission of a relatively low volume of non-delay-sensitive information. As the demand for mobile broadband access continues to increase, however, further improvements in 5G communications technology and beyond may be desired.
For example, for 5G communications technology and beyond, the system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipment (UE). A base station may communicate with UEs on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station).
In a wireless multiple-access communication system, each cell of a network may broadcast synchronization signals for UEs to discover (e.g., primary synchronization signals (PSS), secondary synchronization signals (SSS), etc.). Accordingly, the UEs can synchronize timing and/or frequency to the cell based on the synchronization signals for receiving further communications from (or transmitting communications to) the cell. For example, the UEs can accordingly receive and decode system information from the cell, which can include further information for accessing the cell (e.g., master information blocks (MIB), system information blocks (SIB), etc. over a primary broadcast channel (PBCH) or similar channel).
Wireless communication systems such as a Long Term Evolution (LTE) communication systems or LTE-Advanced (LTE-A) communication systems transmit the synchronization signals over a center channel frequency of the system bandwidth. As LTE uses limited system bandwidth, the UEs can attempt to discover the synchronization signals using a channel raster with multiple channel hypotheses over the system bandwidth. As system bandwidth increases, however, attempts to discover the synchronization signals based on the same channel raster may become burdensome. For example, 5G NR may have wide frequency band deployments, which may increase the number of possible channel hypotheses. Also, downlink cell-specific reference signals (CRS) may not be broadcast at all, or may not be broadcast frequently enough, to facilitate scanning for signals for system acquisition (e.g., especially in a time division duplexing subframe). In addition, using the same channel raster for transmitting signals in LTE and 5G NR may lead to waveform confusion as to which radio access technology is being used where LTE and 5G NR use OFDM-based waveforms on the downlink.